我需要在 Java 中动态创建异步消息队列。我的用例是通过多个 SMTP 服务器发送电子邮件:我需要强制顺序处理发送到同一 SMTP 服务器的电子邮件,但可以同时处理发送到不同 SMTP 服务器的电子邮件。我过去使用过 JMS,但据我所知,它只允许在编译时创建队列,而我需要在运行时创建队列(每个 SMTP 服务器一个队列)。
我是否遗漏了一些关于 JMS 的信息,或者是否有其他一些我应该看看的工具/建议?
最佳答案
我同意 Adam 的观点,这个用例听起来像是 JMS 的开销。足够的 Java 内置功能:
package de.mhaller;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;
import java.util.Queue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.LinkedBlockingDeque;
import org.junit.Assert;
import org.junit.Test;
public class Mailer {
@Test
public void testMailer() throws Exception {
ExecutorService executor = Executors.newCachedThreadPool();
ArrayList<Mail> log = new ArrayList<Mail>();
LinkedBlockingDeque<Mail> incoming = new LinkedBlockingDeque<Mail>();
// TODO: Put mails to be sent into the incoming queue
incoming.offer(new Mail("foo1@localhost", "localhost"));
incoming.offer(new Mail("foo2@otherhost", "otherhost"));
incoming.offer(new Mail("foo3@otherhost", "otherhost"));
incoming.offer(new Mail("foo4@localhost", "localhost"));
Map<Mailserver, Queue<Mail>> queues = new HashMap<Mailserver, Queue<Mail>>();
while (!incoming.isEmpty()) {
Mail mail = incoming.pollFirst();
Mailserver mailserver = findMailserver(mail);
if (!queues.containsKey(mailserver)) {
ArrayDeque<Mail> serverQueue = new ArrayDeque<Mail>();
queues.put(mailserver, serverQueue);
executor.execute(new SendMail(mailserver, serverQueue));
}
Queue<Mail> slot = queues.get(mailserver);
slot.offer(mail);
}
assertMailSentWithCorrectServer(log);
}
private void assertMailSentWithCorrectServer(ArrayList<Mail> log) {
for (Mail mail : log) {
if (!mail.server.equals(mail.sentBy.mailserver)) {
Assert.fail("Mail sent by wrong server: " + mail);
}
}
}
private Mailserver findMailserver(Mail mail) {
// TODO: Your lookup logic which server to use
return new Mailserver(mail.server);
}
private static class Mail {
String recipient;
String server;
SendMail sentBy;
public Mail(String recipient, String server) {
this.recipient = recipient;
this.server = server;
}
@Override
public String toString() {
return "mail for " + recipient;
}
}
public static class SendMail implements Runnable {
private final Deque<Mail> queue;
private final Mailserver mailserver;
public SendMail(Mailserver mailserver, Deque<Mail> queue) {
this.mailserver = mailserver;
this.queue = queue;
}
@Override
public void run() {
while (!queue.isEmpty()) {
Mail mail = queue.pollFirst();
// TODO: Use SMTP to send the mail via mailserver
System.out.println(this + " sent " + mail + " via " + mailserver);
mail.sentBy = this;
}
}
}
public static class Mailserver {
String hostname;
public Mailserver(String hostname) {
this.hostname = hostname;
}
@Override
public String toString() {
return hostname;
}
@Override
public int hashCode() {
return hostname.hashCode();
}
@Override
public boolean equals(Object obj) {
return hostname.equals(((Mailserver) obj).hostname);
}
}
}
关于java - 在 Java 中动态创建异步消息队列,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/1642122/